Janolus savinkini Martynov & Korshunova, 2012

Location: Okawa shita, Osezaki, Shizuoka, Japan
Date: 2017/08/29
Length: 15mm
Depth: 25.0m
Water temperature: 23.0℃

Description

A small to medium-sized janolid, body length up to 30 mm. The body is densely covered by at least 100 large, spindle-shaped, smooth papillae, often attenuated apically (juveniles bear only 30-40 papillae). The notum is completely reduced. The digestive gland is strongly branched and penetrates each papilla as a basal thickening with several narrow branches. Head small, with two short distinct oral tentacles. Rhinophores grouped together with oblique lamellae (up to 20 in adults; 10-15 in juveniles); the caruncle (inter-rhinophoral crest) is well defined with finely branched folds. Foot rounded, with anterior corners absent but strongly bilobed. The anus opens on the right posterior dorsal side. Ground colour creamy yellow with a light orange hue; papillae are the same colour throughout most of their length, with a broad purplish ring near the tip and a bright opaque-blue apical spot; the rhinophores share this colour pattern.

Distribution

Type locality: Mun Island, Nha Trang Bay, Vietnam (22 m depth, sand). Photographic records also from Tre Island and Dung Island, Vietnam. Distributed across the tropical Indo-West Pacific, at 8-38 m depth on various substrata including soft grounds. Specimens previously figured under various provisional names (Janolus sp. or sp. 4 / sp. 7) in earlier field guides and online resources are referable to this species.

Etymology

The specific epithet savinkini honours Oleg Savinkin (Institute of Problem of Evolution and Ecology, Moscow), who contributed for more than three decades to the study, collection and photographing of numerous marine invertebrate and vertebrate species of Vietnam's fauna.

Remarks

Easily distinguished from previously described Janolus species by the unique colour pattern of yellow papillae with a broad purplish subapical band and an opaque-blue apical spot.